The invention relates to a leak-free drinking beaker, comprising a container as well as a lid closing the container, a drink opening which opens into the interior of the container, and a valve, extending over the drink opening, between the drink opening and the container, which valve is held in the closed position under a certain pretension and can be released against said pretension under the influence of a pressure difference.
A drinking beaker of this type is disclosed in WO-A 9708979. The valve used in said beaker is in the form of a membrane in which a slit has been made. When drinking, the slit opens a little so that liquid flows from the drinking beaker. The disadvantage of this known drinking beaker is that the membrane does not seal well. If the drinking beakers falls over or is turned upside down, leakage can still occur as a result of the liquid pressure.
The aim of the invention is to provide a drinking beaker with which freedom from leaks is better guaranteed. This is achieved in that the valve is a double-acting non-return valve, comprising a flexible valve element and two separate valve seats, the valve element and one of the valve seats having a blocking action in a direction opposed to the direction in which the valve element has a blocking action with the other valve seat.
By virtue of the use of a double-acting non-return valve it is possible, on the one hand, to ensure good sealing against leakage whilst, on the other hand, the reduced pressure produced in the drinking beaker by drinking can nevertheless be released. The air that flows in on equalising the reduced pressure can also carry liquid residues back into the beaker, as a result of which subsequent dripping is virtually precluded.
The flexible valve element can be constructed in various ways. According to a simple embodiment, the flexible valve element comprises an annular membrane, one peripheral rim of which interacts with the one valve seat and the other peripheral rim of which interacts with the other valve seat.
The membrane can be a disc which has a central hole, the one valve seat being located opposite the one side of the disc at the outermost rim of the disc and the other valve seat being located opposite the other side of the disc at the innermost rim of the disc. Such a construction is simple and has the advantage that cleaning of the beaker and lid with valve can be carried out easily and reliably.
The two valve seats can be movable with respect to one another in the direction transverse to their plane to change the pretension under which the disc is in contact with the valve seats.
One of the valve seats is formed by that rim of a drinking spout which protrudes inside the lid. The other valve seat is formed by a pin which is coaxial with respect to the other valve seat. With this arrangement the disc is located between the two valve seats and is held in place by the pin which extends to some extent into the interior opening of the disc,
Furthermore, the pin can be movable in the axial direction in order to vary the preloading between disc and valve seats.
The pin is preferably accommodated on a support that is mounted in the lid. Said support can be slidably mounted in the lid in order to vary the mutual spacing of the valve seats and thus the pretension in the valve,
Preferably, the lid has a peripheral rim provided with a screw thread which interacts with a corresponding screw thread on the container, the support being slidable in the axial direction in said peripheral rim. The support interacts with the upper limit of the container such that when the lid is screwed on to the container the pretension between the membrane and the valve seats is adjustable.
Depending on the drink used and/or on the user, it is always possible to set the pretension such that, on the one hand, drinking remains possible, but leaking is prevented.
The peripheral rim has an axial extension which interacts with a sealing ring provided at the periphery of the container, which extension and sealing ring interact with one another over the entire screw region of the screw threads of lid and container.
The support is pretensioned in the direction towards the container.